#include <iostream>

long fibonacci(long n) {
    if (n <= 1) return n;
    return fibonacci(n - 1) + fibonacci(n - 2);
}

int main() {
    long n;
    std::cout << "请输入要计算的 Fibonacci 数字: ";
    std::cin >> n;
    std::cout << fibonacci(n) << std::endl;
    return 0;
}
